This volume, the proceedings of a 1998 international workshop, provides experimental evidence of the effects of correlation on the physical, chemical, and mechanical properties of materials, as well as the theoretical/computational methodology that has been developed for their study.

The study of phase transformations in substitutional alloys, including order disorder phenomena and structural transformations, plays a crucial role in understanding the physical and mechanical properties of materials, and in designing alloys with desired technologically important characteristics. Indeed, most of the physical properties, including equilibrium properties, transport, magnetic, vibrational as well as mechanical properties of alloys are often controlled by and are highly sensitive to the existence of ordered compounds and to the occurrence of structural transformations. Correspondingly, the alloy designer facing the task of processing new high-performance materials with properties that meet specific industrial applications must answer the following question: What is the crystalline structure and the atomic configuration that an alloy may exhibit at given temperature and concentration? Usually the answer is sought in the phase-diagram of a relevant system that is often determined experimentally and does not provide insight to the underlying mechanisms driving phase stability. Because of the rather tedious and highly risky nature of developing new materials through conventional metallurgical techniques, a great deal of effort has been expended in devising methods for understanding the mechanisms contrOlling phase transformations at the microscopic level. These efforts have been bolstered through the development of fully ab initio, accurate theoretical models, coupled with the advent of new experimental methods and of powerful supercomputer capabilities.

It is almost self-evident that surface and interface science, coupled with the electronic structure of bulk materials, playa fundamental role in the understanding of materials properties. If one is to have any hope of understanding such properties as catalysis, microelectronic devices and contacts, wear, lubrication, resistance to corrosion, ductility, creep, intragranular fracture, toughness and strength of steels, adhesion of protective oxide scales, and the mechanical properties of ceramics, one must address a rather complex problem involving a number of fundamental parameters: the atomic and electronic structure, the energy and chemistry of surface and interface regions, diffusion along and across interfaces, and the response of an interface to stress. The intense need to gain an understanding of the properties of surfaces and interfaces is amply attested to by the large number of conferences and workshops held on surface and interface science. Because of this need, the fields of surface and interface science have been established in their own right, although their development presently lags behind that of general materials science associated with bulk, translationally invariant systems. There are good reasons to expect this situation to change rather dramatically in the next few years. Existing techniques for investigating surfaces and interfaces have reached maturity and are increasingly being applied to systems of practical relevance. New techniques are still being created, which drastically widen the scope of applicability of surface and interface studies. On the experimental side, new microscopies are bearing fruit.

It is common practice today to use the term "alloy" in connection with specific classes of materials, with prominence given to metals and semiconductors. However, there is good justification for considering alloys in a unified manner based on properties rather than types of materials because, after all, to alloy means to mix. The scientific aspects of mixing together different materials has a very long history going back to early attempts to understand and control materials behavior for the service of mankind. The case for using the scientific term "alloy" to mean any material consisting of more than one element can be based on the following two considerations. First, many alloys are mixtures of metallic, semiconducting, and/or insulating materials, and the properties of an alloy, i.e., metallic, semiconducting, or insulating, are often functions of composition and of external conditions, such as temperature and pressure. Second, and most importantly, in attempting to understand the various properties of materials, whether physical, chemical, or mechanical, one is apt to use the terminology and experimental, formal, and computational methods in their study that transcend the type of material being studied.

The triennial International Alloy Conferences (lACs) aim at the identification and promotion of the common elements developed in the study, either experimental, phenomenological, or theoretical and computational, of materials properties across materials types, from metals to minerals. To accomplish this goal, the lACs bring together scientists from a wide spectrum of materials science including experiment, theory, modeling, and computation, incorporating a broad range of materials properties. The first lAC, lAC-I, took place in Athens, Greece, June 16-21, 1996. The present volume of proceedings contains the papers presented at IAC-2, that took place in Davos, Switzerland, August 8-13, 1999. The topics in this book fall into several themes, which suggest a number of different classification schemes. We have chosen a scheme that classifies the papers in the volume into the categories Microstructural Properties; Ordering, Kinetics and Diffusion; Magnetic Properties and Elastic Properties. We have juxtaposed apparently disparate of revealing the dynamic character approaches to similar physical processes, in the hope of the processes under consideration. We hope this will invigorate new kinds of discussion and reveal challenges and new avenues to the description and prediction of properties of materials in the solid state and the conditions that produce them.

One of the ultimate goals of materials research is to develop a fun damental and predictive understanding of the physical and metallurgical properties of metals and alloys. Such an understanding can then be used in the design of materials having novel properties or combinations of proper ties designed to meet specific engineering applications. The development of new and useful alloy systems and the elucidation of their properties are the domain of metallurgy. Traditionally, the search for new alloy systems has been conducted largely on a trial and error basis, guided by the skill and intuition of the metallurgist, large volumes of experimental data, the principles of 19th century thermodynamics and ad hoc semi-phenomenological models. Recently, the situation has begun to change. For the first time, it is possible to understand the underlying mechanisms that control the formation of alloys and determine their properties. Today theory can begin to offer guidance in predicting the properties of alloys and in developing new alloy systems. Historically, attempts directed toward understanding phase stability and phase transitions have proceeded along distinct and seemingly diverse lines. Roughly, we can divide these approaches into the following broad categories. 1. Experimental determination of phase diagrams and related properties, 2. Thermodynamic/statistical mechanical approaches based on semi phenomenological models, and 3. Ab initio quantum mechanical methods. Metallurgists have traditionally concentrated their efforts in cate gories 1 and 2, while theoretical physicists have been preoccupied with 2 and 3."

Engineering materials with desirable physical and technological properties requires understanding and predictive capability of materials behavior under varying external conditions, such as temperature and pressure. This immediately brings one face to face with the fundamental difficulty of establishing a connection between materials behavior at a microscopic level, where understanding is to be sought, and macroscopic behavior which needs to be predicted. Bridging the corresponding gap in length scales that separates the ends of this spectrum has been a goal intensely pursued by theoretical physicists, experimentalists, and metallurgists alike. Traditionally, the search for methods to bridge the length scale gap and to gain the needed predictive capability of materials properties has been conducted largely on a trial and error basis, guided by the skill of the metallurgist, large volumes of experimental data, and often ad hoc semi phenomenological models. This situation has persisted almost to this day, and it is only recently that significant changes have begun to take place. These changes have been brought about by a number of developments, some of long standing, others of more recent vintage.

The handling of actinides and actinide-based materials provides significant technological challenges due to the toxicity and radioactivity associated with these materials. These challenges are particularly apparent in the nuclear power industry. Under normal operation, a reactor can produce a significant amount of spent fuel requiring subsequent containment for geologic times, and under accident conditions it can release lethal doses of radioactive material to the environment. Inevitably, radioactive material will enter the environment, necessitating as complete an understanding as possible of its behavior. An understanding of the interaction between actinides and the environment must be based on a knowledge of their basic physical and chemical properties. To date, although there is general agreement on the principles for waste disposal, no facility has been built for the long term disposal of high level radioactive waste from either normal reactor operations or from accidental catastrophes. This makes it most important for the scientific and technical community to develop the necessary cross-disciplinary understanding that will help us implement safe and secure waste management, accident remediation and accident prevention systems.

This is the second in a series of "International Workshops on Electron Correlations and Materials Properties. " The aim of this series of workshops is to provide a periodic (triennial) and in-depth assessment of advances in the study and understanding of the effects that electron-electron interactions in solids have on the determination of measurable properties of materials. The workshop is structured to include exposure to experimental work, to phenomenology, and to ab initio theory. Since correlation effects are pervasive the workshop aims to concentrate on the identification of promising developing methodology, experimental and theoretical, addressing the most critical frontier issues of electron correlations on the properties of materials. This series of workshops is distinguished from other topical meetings and conferences in that it strongly promotes an interdisciplinary approach to the study of correlations, involving the fields of quantum chemistry, physics, and materials science. The First Workshop was held June 28-July 3, 1998, and a proceedings of the workshop was published by KluwerlPlenum. The Second Workshop was held June 24- 29,2001, and this volume contains the proceedings of that scientific meeting. Through the publications of proceedings, the workshop attempts to disseminate the information gathered during the discussions held at the Workshop to the wider scientific community, and to establish a record of advances in the field.

The triennial International Alloy Conferences (lACs) aim at the identification and promotion of the common elements developed in the study, either experimental, phenomenological, or theoretical and computational, of materials properties across materials types, from metals to minerals. To accomplish this goal, the lACs bring together scientists from a wide spectrum of materials science including experiment, theory, modeling, and computation, incorporating a broad range of materials properties. The first lAC, lAC-I, took place in Athens, Greece, June 16-21, 1996. The present volume of proceedings contains the papers presented at IAC-2, that took place in Davos, Switzerland, August 8-13, 1999. The topics in this book fall into several themes, which suggest a number of different classification schemes. We have chosen a scheme that classifies the papers in the volume into the categories Microstructural Properties; Ordering, Kinetics and Diffusion; Magnetic Properties and Elastic Properties. We have juxtaposed apparently disparate of revealing the dynamic character approaches to similar physical processes, in the hope of the processes under consideration. We hope this will invigorate new kinds of discussion and reveal challenges and new avenues to the description and prediction of properties of materials in the solid state and the conditions that produce them.

This volume, the proceedings of a 1998 international workshop, provides experimental evidence of the effects of correlation on the physical, chemical, and mechanical properties of materials, as well as the theoretical/computational methodology that has been developed for their study.

The handling of actinides and actinide-based materials provides significant technological challenges due to the toxicity and radioactivity associated with these materials. These challenges are particularly apparent in the nuclear power industry. Under normal operation, a reactor can produce a significant amount of spent fuel requiring subsequent containment for geologic times, and under accident conditions it can release lethal doses of radioactive material to the environment. Inevitably, radioactive material will enter the environment, necessitating as complete an understanding as possible of its behavior. An understanding of the interaction between actinides and the environment must be based on a knowledge of their basic physical and chemical properties. To date, although there is general agreement on the principles for waste disposal, no facility has been built for the long term disposal of high level radioactive waste from either normal reactor operations or from accidental catastrophes. This makes it most important for the scientific and technical community to develop the necessary cross-disciplinary understanding that will help us implement safe and secure waste management, accident remediation and accident prevention systems.

The primary goal of a materials scientist is a predictive understanding of materials properties and that requires a clear picture of the role played by electrons in determining the materials' behavior. Only then can one hope to design and build new materials with desired physical, chemical and engineering characteristics. Research is carried out on the basis of quantum mechanics, through solution of the so-called single-particle Schroedinger equation that describes the behavior of electrons in a solid. This book describes one formal approach to solving the Schroedinger equation developed within the framework of multiple scattering theory (MST). It offers a comprehensive and welcome entree to the field of electronic structure of solids and should serve as a treatise for advanced undergraduates, graduate students and researchers in the field. Topics Include: concepts and formalism; periodic solids and impurities; substitutional alloys; surfaces and interfaces; transport; phonons and photons and formal Green-function theory.

One of the ultimate goals of materials research is to develop a fun­ damental and predictive understanding of the physical and metallurgical properties of metals and alloys. Such an understanding can then be used in the design of materials having novel properties or combinations of proper­ ties designed to meet specific engineering applications. The development of new and useful alloy systems and the elucidation of their properties are the domain of metallurgy. Traditionally, the search for new alloy systems has been conducted largely on a trial and error basis, guided by the skill and intuition of the metallurgist, large volumes of experimental data, the principles of 19th century thermodynamics and ad hoc semi-phenomenological models. Recently, the situation has begun to change. For the first time, it is possible to understand the underlying mechanisms that control the formation of alloys and determine their properties. Today theory can begin to offer guidance in predicting the properties of alloys and in developing new alloy systems. Historically, attempts directed toward understanding phase stability and phase transitions have proceeded along distinct and seemingly diverse lines. Roughly, we can divide these approaches into the following broad categories. 1. Experimental determination of phase diagrams and related properties, 2. Thermodynamic/statistical mechanical approaches based on semi­ phenomenological models, and 3. Ab initio quantum mechanical methods. Metallurgists have traditionally concentrated their efforts in cate­ gories 1 and 2, while theoretical physicists have been preoccupied with 2 and 3.